Overview

We were eager to start recovering our moorings, but the sea is pretty choppy today, so we are going to wait until tomorrow. While we’re waiting, we thought we’d give you a little refresher as to what we are doing out here so that you know what to expect in the coming weeks.

As you may recall, last year we deployed six acoustic sources and a Distributed Vertical Line Array (DVLA) in the Philippine Sea. The map shows the locations of the 6 sources and the DVLA. Right now we are at he location of Source 5. The DVLA consists of approximately 5km of wire with 150 hydrophones (underwater microphones) attached to it. Each of the six source moorings also has a smaller array with four hydrophones on it. All of the moorings are anchored to the bottom and held vertical by a subsurface buoy. The basic idea is to transmit sound back and forth between the different sources to map out the temperature and currents of the ocean in between the moorings. Check out our earlier post “An ocean acoustic tomography experiment” for more info.

The sources have been out here transmitting and collecting data for almost a year now, so we are going to go pick up the moorings one by one and start downloading the data. We are also going to be making some of the same types of measurements we made during our last cruise. For example, we plan to make more maps of the ocean floor between our moorings (see our post Sounding Out the Ocean’s Depths) and we will be doing some more CTDs (see our post Good Morning CTD). In addition we have a couple other exciting side projects that are going on during this cruise as well. We will be recovering a couple acoustic seagliders, which are underwater robots that have been listening to the sources and measuring temperature and salinity in the upper ocean. We'll also be sampling some mud from the bottom of the ocean!